Strobilurins are widely used in agriculture as fungicides. They belong to the QoIfamily of fungicides and are used to control a wide array of fungal diseases caused by water moulds, downy mildews, powdery mildews, leaf spotting and blighting fungi, fruit rotters, and rusts. QoI fungicides are chemical compounds that act at the Quinol outer binding site of the cytochrome bc1 complex, inhibiting fungal mitochondrial respiration that stops energy production in the fungus and results in its death. The strobilurins are used on a wide variety of crops including cereals, field crops, fruits, tree nuts, vegetables, turfgrass and ornamentals. Most strobilurins show weak systemic activity, and are useful—to varying degrees—as protectant, curative and translaminar fungicides (ref: Balba, H. J. Envi. Sci. Heath. Part B. 2007, 42, 441. As an example, azoxystrobin shows good protective yet mild curative properties due to its weak systemic properties. A useful formulation would mitigate these drawbacks of the fungicide and ideally provide excellent protectant and curative properties, so that it can both protect a crop from fungal infection and eradicate the infection after it is established. Because strobilurins target only a single metabolic pathway in the fungus, there are instances where mutations can occur in certain species that can make them resistant to strobilurins. It is therefore also useful to create strobilurin formulations that can easily be mixed with fungicides that have other modes of action to minimize the spread of strobilurin resistant strains.
Strobilurins are nonpolar compounds, have relatively low water solubility (on the scale of ug/Lg/L), low volatility, and have moderate to low soil mobility. Strobilurins can vary in their stability towards hydrolysis and photolysis under natural environmental conditions where pH and temperature contribute to their chemical degradation. There is further a need to create formulations that can extend the effective lifetime of strobilurins and related compounds by reducing their susceptibly towards chemical degradation both before and after the formulation has been applied in the field.
Strobilurins are currently formulated into various usable forms such as emulsifiable concentrates (ECs), liquid concentrate (SL), and suspension concentrates (SC) that use petroleum or non-petroleum based solvents along with anionic and non-ionic emulsifiers and stabilizers. Strobilurins have also been formulated as water dispersible powders or granules (WPs or WGs) and soluble powders (SP) that use organic or inorganic carriers. These formulations are available as solid or liquid formulations with varying contents of active ingredient (low or high) that can be used as is or after dilution with water. As described below, while these formulations address some of the inherent challenges that are associated with strobilurins there remains a need in the art for improved strobilurin formulations.